Nutrition

Dioscorea is a major food staple throughout Africa and tropical regions with reports of providing at least 200 dietary calories to 300 million people in the tropics and up to 552 calories daily in Cote d’Ivoire. Of the 600+ varieties of yam, however, there is only a comparative handful (50-60) that are cultivated or gathered for food or pharmaceutical purposes. The most significant food crops economically are as follows:

Other notable sought-after species of wild yam include D. preanhensilis, D. abyssinca, D. burkilliana, D. mangenotiana, and D. togoensis. Beyond being calorically dense, yams are a source of Vitamins C and B6, potassium, iron, and manganese with low levels of salt and saturated fats (see USDA National Nutrient Database Record for Dioscorea), thereby lending itself to protecting against malnourishment-related diseases such as Kwashiorkor, goiter, dwarfism, and Konzo (spastic paralysis). Compared to cassava, yam also has an eight-fold supply of protein as well as not threatening cyanide poisoning if cooked improperly. Unfortunately, besides threatening yields, fungal pathogens also reduce yams’ nutritional value, particularly Asperigillus niger and Botriodiploida theobromae which are the most destructive. With only ~10% of yam varieties being edible, D. alata, D. cayensis, and D. rotundata are the most frequently consumed varieties; however, D. esculenta has been reported as the most nutritious. Meanwhile, D. dumetorum, a bitter yam, is a ‘famine crop’ that is eaten in times of food scarcity and requires soaking and cooking before eating.

Food Applications

Like other starchy tubers, yams can be boiled, baked, roasted, mashed, fried, etc. Classic dishes with yam include amala, foutou, fufu, and pounded yam (see recipes). Paulus et. al. (2013) also reported the use of shoots and leaves for consumption. Yams are also frequently made into flours or elubo, a slightly fermented flour for longer storage. Traditionally, varieties of ‘harder’ yams that are more resistant to pests and higher yielding maintain characteristics good for flours while softer yams are more preferred for their sweetness. While yam flours alone cannot make glutenous breads, they can be substituted at up tp 30% in wheat flours to still meet customer satisfaction. Significantly, yam flours have a low glycemic content (for preventing diabetes). Dioscorea also responds favorably to acid modification which makes it conducive to large-scale food applications. Various species also boast properties conducive to large-scale food applications including D. alata for ready-to-eat snacks, D. dumetorum for paste and infant formulas, and D. cayensis and D. rotundata for higher elasticity products.

Relevant External Sources